Since the return of the wolf to Yellowstone in 1995, there has been no lack of interesting dynamics to observe and study. From pack rivalries, to changing territories, and the significant fluctuation of wolf population numbers, the Yellowstone wolves are always fascinating to watch.

This year, one of the most interesting stories to follow is that of the Mollie’s Pack. Over the winter, the pack shifted their movements to the Lamar Valley and adjacent areas of the Northern Range. For the time being, they have assumed a similar territory once occupied by their reintroduced Canadian ancestors upon release from their acclimation pen south of Slough Creek in 1995.

Although the Mollie's Pack has made annual trips to the Northern Range in previous years, they usually only stayed for a few days each visit. This year marks their greatest presence in more than 16 years; as of early May 2012, they have occupied the area for a combined total of 100 days.

This Lamar Valley territory was inhabited until recently by the legendary – and now defunct – Druid Peak Pack, which had battled for and won the Lamar territory from the Crystal Creek Pack, now renamed Mollie’s Pack*, in 1996. The Crystal Creek alpha male was killed during that battle, forcing the pack to retreat. The Crystal Creek/Mollies eventually settled into the interior of the park, with the core of their territory the Pelican Valley. During their occasional visits back up to the Northern Range, there were times when they fought with the Druid wolves.

“In the years after the 1996 battle, I often wondered if there would come a time when the descendants of the Crystal Creek/Mollie’s Pack might return to the Northern Range and attempt to reclaim their ancestral territory,” said Rick McIntyre, biological technician for the Yellowstone Wolf Project.

It remains to be seen, says McIntyre, whether the Mollies will stay on the Northern Range long-term, or whether they will return to the Pelican Valley once prey starts to come back this summer.

The Northern Range is considered prime wolf habitat, with ample herds of prey, and less snowfall than the interior of the park. If they decide to stay, because the Mollie's Pack is currently the largest in the park, the other Northern Range packs will find it challenging to cope with their presence.

“Wolves aggressively defend their families and territories, frequently being killed in the process. The Yellowstone Wolf Project has found that the most common cause of death for adult wolves living in the park is being killed by other wolves. This is a major factor that controls the number of wolves here in Yellowstone,” added McIntyre.

There are currently around 85 wolves, in ten packs, in Yellowstone. The Mollie's Pack has 17 members, five of which are collared.

The Yellowstone Park Foundation, a nonprofit, 501(c)3 organization, works in cooperation with the National Park Service to fund projects and programs that protect, preserve, and enhance the natural and cultural resources and the visitor experience of Yellowstone National Park.